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Amoxicillin
Pronunciation
U.S. Brand Names
Generic Available
Canadian Brand Names
Synonyms
Pharmacological Index
Use
Pregnancy Risk Factor
Contraindications
Warnings/Precautions
Adverse Reactions
Overdosage/Toxicology
Drug Interactions
Stability
Mechanism of Action
Pharmacodynamics/Kinetics
Usual Dosage
Dietary Considerations
Monitoring Parameters
Test Interactions
Mental Health: Effects on Mental Status
Mental Health: Effects on Psychiatric Treatment
Dental Health: Local Anesthetic/Vasoconstrictor Precautions
Dental Health: Effects on Dental Treatment
Patient Information
Nursing Implications
Dosage Forms
References

Pronunciation
(a moks i SIL in)

U.S. Brand Names
Amoxil®; Biomox®; Trimox®; Wymox®

Generic Available

Yes


Canadian Brand Names
Apo®-Amoxi; Novamoxin®; Nu-Amoxi; Pro-Amox®

Synonyms
Amoxicillin Trihydrate; Amoxycillin; p-Hydroxyampicillin

Pharmacological Index

Antibiotic, Penicillin


Use

Dental: Antibiotic for standard prophylactic regimen for dental patients who are at risk

Medical: Treatment of otitis media, sinusitis, and infections caused by susceptible organisms involving the respiratory tract, skin, and urinary tract; prophylaxis of bacterial endocarditis in patients undergoing surgical or dental procedures; approved in combination with clarithromycin and lansoprazole for eradication of H. pylori; in patients with active duodenal ulcer disease or a 1-year history of duodenal ulcer. The combined use of lansoprazole and amoxicillin is approved for patients unable to take clarithromycin.


Pregnancy Risk Factor

B


Contraindications

Hypersensitivity to amoxicillin, penicillin, or any component


Warnings/Precautions

In patients with renal impairment, doses and/or frequency of administration should be modified in response to the degree of renal impairment; a high percentage of patients with infectious mononucleosis have developed rash during therapy with amoxicillin; a low incidence of cross-allergy with other beta-lactams and cephalosporins exists


Adverse Reactions

1% to 10%:

Central nervous system: Fever

Dermatologic: Urticaria, rash

Miscellaneous: Allergic reactions (includes serum sickness, rash, angioedema, bronchospasm, hypotension, etc)

<1%: Seizures, anxiety, confusion, hallucinations, depression (with large doses or patients with renal dysfunction), nausea, vomiting, leukopenia, neutropenia, thrombocytopenia, jaundice, interstitial nephritis


Overdosage/Toxicology

Symptoms of penicillin overdose include neuromuscular hypersensitivity (agitation, hallucinations, asterixis, encephalopathy, confusion, and seizures) and electrolyte imbalance with potassium or sodium salts, especially in renal failure

Hemodialysis may be helpful to aid in the removal of the drug from the blood, otherwise most treatment is supportive or symptom directed


Drug Interactions

Decreased effect: Efficacy of oral contraceptives may be reduced

Increased effect: Disulfiram, probenecid may increase amoxicillin levels

Increased toxicity: Allopurinol theoretically has an additive potential for amoxicillin rash


Stability

Oral suspension remains stable for 7 days at room temperature or 14 days if refrigerated; unit dose antibiotic oral syringes are stable for 48 hours


Mechanism of Action

Inhibits bacterial cell wall synthesis by binding to one or more of the penicillin binding proteins (PBPs); which in turn inhibits the final transpeptidation step of peptidoglycan synthesis in bacterial cell walls, thus inhibiting cell wall biosynthesis. Bacteria eventually lyse due to ongoing activity of cell wall autolytic enzymes (autolysins and murein hydrolases) while cell wall assembly is arrested.


Pharmacodynamics/Kinetics

Absorption: Oral: Rapid and nearly complete; food does not interfere

Distribution: Widely distributed to most body fluids and bone; penetration into cells, eyes, and across normal meninges is poor

Protein binding: 17% to 20%

Ratio of CSF to blood: Normal meninges: <1%; Inflamed meninges: 8% to 90%

Metabolism: Partial

Half-life:

Neonates, full-term: 3.7 hours

Infants and Children: 1-2 hours

Adults with normal renal function: 0.7-1.4 hours

Patients with Clcr <10 mL/minute: 7-21 hours

Time to peak: 2 hours (capsule) and 1 hour (suspension)

Elimination: Renal excretion (80% as unchanged drug); lower in neonates


Usual Dosage

Oral:

Subacute bacterial endocarditis prophylaxis: 50 mg/kg 1 hour before procedure

Adults: 250-500 mg every 8 hours or 500-875 mg twice daily; maximum dose: 2-3 g/day

Endocarditis prophylaxis: 2 g 1 hour before procedure

Helicobacter pylori: 250-500 mg 3 times/day or 500-875 mg twice daily; clinically effective treatment regimens include triple therapy with amoxicillin or tetracycline, metronidazole, and bismuth subsalicylate; amoxicillin, metronidazole, and an H2-receptor antagonist; amoxicillin, lansoprazole, and clarithromycin.

Dosing interval in renal impairment:

Clcr 10-50 mL/minute: Administer every 12 hours

Clcr <10 mL/minute: Administer every 24 hours

Dialysis: Moderately dialyzable (20% to 50%) by hemo- or peritoneal dialysis; approximately 50 mg of amoxicillin per liter of filtrate is removed by continuous arteriovenous or venovenous hemofiltration (CAVH); dose as per Clcr <10 mL/minute guidelines


Dietary Considerations

Food: May be taken with food


Monitoring Parameters

With prolonged therapy, monitor renal, hepatic, and hematologic function periodically; assess patient at beginning and throughout therapy for infection; monitor for signs of anaphylaxis during first dose


Test Interactions

May interfere with urinary glucose tests using cupric sulfate (Benedict's solution, Clinitest®); may inactivate aminoglycosides in vitro


Mental Health: Effects on Mental Status

Rarely large doses may produce confusion, hallucinations, and depression; penicillins have been reported to cause apprehension, illusions, agitation, insomnia, depersonalization, and encephalopathy


Mental Health: Effects on Psychiatric Treatment

Disulfiram may increase amoxicillin levels


Dental Health: Local Anesthetic/Vasoconstrictor Precautions

No information available to require special precautions


Dental Health: Effects on Dental Treatment

Prolonged use of penicillins may lead to development of oral candidiasis


Patient Information

Take entire prescription, even if you are feeling better. Take at equal intervals around-the-clock; may be taken with milk, juice, or food. You may experience nausea or vomiting (small frequent meals, frequent mouth care, sucking lozenges, or chewing gum may help). If diabetic, drug may cause false tests with Clinitest® urine glucose monitoring; use of glucose oxidase methods (Clinistix®) or serum glucose monitoring is preferable. This drug may interfere with oral contraceptives; an alternate form of birth control should be used. Report rash; unusual diarrhea; vaginal itching, burning, or pain; unresolved vomiting or constipation; fever or chills; unusual bruising or bleeding; or if condition being treated worsens or does not improve by the time prescription is completed.


Nursing Implications

Assess patient at beginning and throughout therapy for infection; observe for signs and symptoms of anaphylaxis; obtain specimens for C&S before the first dose; administer around-the-clock rather than 3 times/day, etc, (ie, 8-4-12, not 9-1-5) to promote less variation in peak and trough serum levels

With prolonged therapy, monitor renal, hepatic, and hematologic function periodically


Dosage Forms

Capsule, as trihydrate: 250 mg, 500 mg

Powder for oral suspension, as trihydrate: 125 mg/5 mL (5 mL, 80 mL, 100 mL, 150 mL, 200 mL); 250 mg/5 mL (5 mL, 80 mL, 100 mL, 150 mL, 200 mL)

Powder for oral suspension, drops, as trihydrate: 50 mg/mL (15 mL, 30 mL)

Suspension, oral: 200 mg/5 mL; 400 mg/5 mL

Tablet, chewable, as trihydrate: 125 mg, 200 mg, 250 mg, 400 mg

Tablet, film coated: 500 mg, 875 mg


References

Boguniewicz M and Leung DY, "Hypersensitivity Reactions to Antibiotics Commonly Used in Children," Pediatr Infect Dis J, 1995, 14(3):221-31.

Canafax, DM, Yuan Z, Chonmaitree T, et al, "Amoxicillin Middle Ear Fluid Penetration and Pharmacokinetics in Children with Acute Otitis Media," Pediatr Infect Dis J, 1998, 17(2):149-56.

Dajani AS, Taubert KA, Wilson WW, et al, "Prevention of Bacterial Endocarditis. Recommendations by the American Heart Association," JAMA 1997, 277(22):1794-801.

Donowitz GR and Mandell GL, "Beta-Lactam Antibiotics," N Engl J Med, 1988, 318(7):419-26 and 318(8):490-500.

Dougall HT, et al, "The Effect of Amoxicillin on Salivary Nitrite Concentrations: An Important Mechanism of Adverse Reactions?" Br J Clin Pharmacol, 1995, 39(4):460-2.

Hautekeete ML, Brenard R, Horsmans Y, et al, "Liver Injury Related to Amoxycillin-Clavulanic Acid: Interlobular Bile-Duct Lesions and Extrahepatic Manifestations," J Hepatol, 1995, 22(1):71-7.

Hill S, Yeates M, Pathy J, et al, "A Controlled Trial of Norfloxacin and Amoxicillin in the Treatment of Uncomplicated Urinary Tract Infection in the Elderly," J Antimicrob Chemother, 1985, 15(4):505-6.

Jones KH and Hill SA, "The Toxicology, Absorption and Pharmacokinetics of Amoxicillin," Adv Clin Pharmacol, 1974, 7:20.

Oe PL, et al, "Pharmacokinetics of the New Penicillins, Amoxicillin and Flucloxacillin in Patients With Terminal Renal Failure Undergoing Hemodialysis," Chemotherapy, 1973, 19:279.

Parry MF, "The Penicillins," Med Clin North Am, 1987, 71(6):1093-112.

Prignet JM, Galzin M, Duval JL, et al, "Amoxicillin-Induced Esophageal Ulcer With Intractable Hiccups as the Presenting Manifestation," Semaine des Hopitaux, 1995, 71:186-7.

Westphal JF, Jehl F, Brogard JM, et al,"Amoxicillin Intestinal Absorption Reduction by Amiloride: Possible Role of the Na+-H+ Exchanger," Clin Pharmacol Ther, 1995, 57(3):257-64.

Wright AJ, "The Penicillins," Mayo Clin Proc, 1999, 74(3):290-307.

Wynn RL, "Amoxicillin Update," Gen Dent, 1991, 39(5):322,4,6.


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